The invention disclosed herein relates to the field of thermal packs. In particular, the invention relates to thermal packs wherein reduced or elevated temperatures can be generated for extended periods of time.
The use of thermally reactive chemical systems in thermal packs is known. Typical uses of hot and cold packs include thermal therapy for treatment of muscle soreness, injuries such as sprains, maintenance of food and beverage temperature, and the like. The treatment of injuries or sore muscles using a hot pack is generally referred to as xe2x80x9cwarm therapyxe2x80x9d or xe2x80x9cheat therapyxe2x80x9d, and the treatment using a cold pack is generally referred to as xe2x80x9ccold therapyxe2x80x9d. In the case of cold therapy, because the swelling associated with the injury or sore muscle begins almost immediately with the onset of injury, or the stress inducing the soreness, treatment should begin promptly. Conditions which benefit from heat therapy include hypothermia and thermal shock. Accordingly, it is desirable that whatever the source of thermal therapy used for such treatment, the thermal therapy source should be readily available, easy to use, and capable of providing thermal therapy for a duration that is effective in treating the injury, sore muscle or condition.
Several general types of thermal packs are known in the art. There are cold packs that contain an insulating material which, upon cooling in a refrigerator or freezer, gradually warm back to ambient temperature. Likewise, there are hot packs which contain an insulating material and are heated to a temperature which gradually cool to ambient temperature. There are hot and cold packs that operate via phase change of the thermal pack components. Also, there are thermal packs that employ chemical components that dissolve endothermically or exothermically in a solvent.
Examples of cold packs that employ an insulating material include cold packs that contain gelling agents, such as the thermal packs described in Williams U.S. Pat. No. 3,804,077 and Dunshee et al. U.S. Pat. No. 4,462,224. For example, these cold packs are cooled in a refrigerator or freezer. Once cooled, the cold pack is placed on the injured or sore area and thus provides cold therapy. Typical gels used in this type of cold pack are based on the gelation of xanthan gum, locust bean gum, gum tragacanth, guar gum, hydroxypropyl methylcellulose, absorbent poylmers, and the like. Gels may also be based on a high molecular weight polyacrylic acid cross-linked with a polyalkenyl ether, also referred to as cis-carbomers.
Other examples of cold packs that employ an insulating material exist in the art. For example, cold packs may employ an outer insulative layer. Alternatively, clays or silicates can be used in conjunction with cold therapy providing chemicals to form aqueous colloidal dispersions sometimes referred to as gels. These colloidal dispersions perform a similar life-extending function due to steric hindrance provision during dissolution.
Phase change materials can be converted between solid and liquid phases and utilize their latent heat of fusion to cool or heat during such phase conversion. The latent heats of fusion are greater than the sensible heat capacities of the materials. Accordingly, the amount of energy absorbed upon melting or released upon freezing is greater than the amount of energy absorbed or released upon increasing or decreasing the temperature of the material by 10xc2x0 C. within a phase. Water or the silica based materials described in Salyer U.S. Pat. No. 5,211,949 are examples of phase change materials.
Certain chemical compounds, once dissolved into a solution, result in a lowering of the temperature of the solution below ambient temperature. On dissolution, these compounds take up heat from the surrounding environment. For example, inorganic salts or soluble organic compounds known to have a positive (greater than zero) enthalpy (xcex94sol Hxc2x0) of aqueous solution are used to make the reduced temperature solutions useful in cold packs. However, solvents other than water can be used so long as xcex94sol Hxc2x0 of the solute is greater than zero. Similarly, there are also chemical compounds which upon dissolving in solution result in elevated temperatures above ambient temperature including inorganic salts or soluble organic compounds known to have a negative (less than zero) enthalpy (xcex94sol Hxc2x0) of aqueous solution. These compounds are used to make elevated temperature solutions useful in hot packs. Other ingredients can be added to these compounds as well. For example, alternative solvents can be used in hot packs.
Any of these types of thermal packs can be used in combination with one another. For example, cold packs which employ a gel can also contain endotherm-producing compounds. Phase change materials can also be used in combination with endotherm-producing compounds or exotherm-producing compounds.
One problem associated with conventional thermal packs is the short duration of the temperature effect. To be useful in thermal therapy, the thermal pack must provide the desired temperature effect for a period of time needed for the particular therapy or use.
Thermal packs of the type that employ thermally reactive chemicals have employed various methods to extend the cold duration or the xe2x80x9clifexe2x80x9d of the thermal pack. Methods of extending the life of thermal packs can be summarized into three categories: 1) physical means to slow dissolution of the endotherm-producing or exotherm-producing chemical; 2) temperature means to provide a large temperature differential with respect to an ambient temperature; and 3) insulation means to control the rate of heat absorption or retention in an attempt to increase the time the thermal pack is at a desired temperature.
Physical means to slow dissolution of the endotherm-producing and exotherm-producing chemicals can use coated solutes whereby the coating slows dissolution. Thermal packs of this type have also used endotherm-producing or exotherm-producing chemicals pressed into pellets. For example, coated particles which control the reaction rate in cool packs are described in Lahey et al. U.S. Pat. No. 4,780,117. The pellet-form slows the dissolution of the endotherm-producing chemical and thus prolongs the life of the cold pack.
The second category wherein temperature means is used to provide a large temperature differential with respect to an ambient temperature operates by increasing temperature differential and thereby increasing the time required for the cold pack to return to ambient temperature. For example, the large temperature differential can be accomplished by using one or two endotherm-producing chemicals whereby one of the chemicals reduces temperature to an extremely low value and the other reduces the temperature to one which is useful for cold therapy. Similarly, two exotherm-producing chemicals, or a combination of one exothermic and one endothermic chemical, have been used to maintain usable temperature ranges.
Thermal packs which employ gelling agents are included in the third category of methods for extending the life of cold and hot packs. The gelling agents can be included in the same container as the endotherm-producing or exotherm-producing chemical. One example of a typical gelling agent is hydroxypropylmethylcellulose. When initiated, the endotherm-producing chemical reduces the temperature of the cold pack and the gelling agent gels. The formed gel provides some level of dissolution hindrance so the rate of dissolution is decreased.
Thermal device structures have also been explored as a means to extend the life of thermal packs. One such device is described in Brown et al., U.S. Pat. No. 5,603,729, wherein a prolonged reaction thermal device having three compartments and thermally reactive ingredients is described. A solvent is separated from two water-dissolving containers each containing ammonium nitrate and having varying thickness to control the rate of dissolution. The extended life, however, is the result of the rate of dissolving of the solute-containing pouches.
Each of the above thermal packs and methods of extending life thereof have proven to be unreliable, uncontrolled, or cumbersome. Many conventional cold packs and hot packs produce a useful temperature for a relatively short duration. Therefore, the thermal pack may be ineffective in providing adequate thermal therapy or maintenance of food or beverages at appropriate temperature levels. Attempts to extend the reduced temperature duration have presented problems. If the means to extend the life of the thermal pack is based on using a large initial temperature differential, the pack will most likely generate an unsuitable temperature for its intended use. This is especially important in therapeutic applications of the thermal packs.
It is generally understood that a thermal pack will maintain a temperature for increasing amounts of time as the concentration of thermal chemical increases. It is also generally understood that many endotherm-producing and exotherm-producing chemicals are salts. Generally, thermal packs which employ endothermic or exothermic salts are used only one at a time, and once the pack has attained a temperature at which it is no longer useful, it is thrown away. Certain disposal regulations, however, limit the amount of these endotherm-producing and exotherm-producing salts used in thermal packs. The concentration of these salts, therefore, cannot be increased without limit.
What would be advantageous, therefore would be a thermal pack having an extended life which does not require the use of potentially costly insulting means. Even more advantageous would be a thermal pack which provides extended life at a usable or suitable temperature and which employs salt concentrations that comply with regulatory requirements. Furthermore, a thermal pack wherein the extended life is the combined result of both chemical factors as well as the user""s ability to control the timing of the thermal reaction or sequential thermal reactions would be particularly useful.
The invention provides for a thermal pack (i.e., hot or cold pack) with an extended life wherein the desired temperature for its intended application is maintained. In other words, the thermal pack of the invention employs a temperature differential with respect to ambient temperature appropriate for its intended application initially and through the duration of its use. Furthermore, the method for extending life of the thermal pack of the invention is independent of particle size or coatings, or additional insulation techniques. Instead, the thermal packs of the invention not only afford extended life by controlling the saturation of the solvent, but also provide the user with the ability to control the initiation of sequential thermal reactions as well and thus xe2x80x9cregeneratingxe2x80x9d the pack in accordance with the user""s particular preferences or needs.
The invention provides a thermal pack comprising a solvent and at least two solutes (first and second endotherm-producing chemicals in the case of a cold pack or first and second exotherm-producing chemicals in the case of hot packs), wherein the solutes are chemically separated until time of use. Thermal packs according to the invention comprise at least three compartments which chemically separate the solvent and each of the solutes from one another. The extended life, or duration of thermal effect, of a thermal pack in accordance with the invention is afforded by the chemical reaction between the solvent and the simultaneous or sequential combination of the two different solutes alone separated from one another until time of use, in conjunction with the structure of the thermal pack components. In other words, thermal pack structural features can be used to control the temperature and duration of the thermal effect in addition to the chemical aspects of the thermal pack, i.e., selection of the thermally reactive chemicals to control the useful temperature and extend the life of the thermal pack. Furthermore, the chemical separation of the solutes from one another until time of use prevents undesired chemical reactions between the solutes which can occur as a result of chemical incompatibility and storage conditions.
The invention provides for a thermal pack adapted to extend the duration of thermal effect comprising: a container sealed to the atmosphere; a first thermally reactive chemical solute disposed within said container; a rupturable solvent packet disposed within said container; a solvent disposed within said solvent packet; a rupturable solute packet disposed within said container; a second thermally reactive chemical solute disposed within said solute packet; wherein each of the solvent, and each of the first and second thermally reactive solutes are chemically separated and wherein the first thermally reactive solute is different from the second thermally reactive solute.
Another embodiment of the invention provides for a thermal pack adapted to extend the duration of thermal effect comprising: a container sealed to the atmosphere; a first thermally reactive chemical solute disposed within said container; a rupturable solvent packet disposed within said container; a solvent disposed within said solvent packet; a first rupturable solute packet disposed within said container; a second thermally reactive chemical solute disposed within said first rupturable solute packet; a second rupturable solute packet disposed within said container; a third thermally reactive chemical solute disposed within said second rupturable solute packet; wherein each of the solvent, first, second and third thermally reactive solutes are chemically separated and wherein at least two of the first, second and third thermally reactive solutes are different from each other.
In yet a further embodiment, the invention provides for a thermal pack adapted to extend the duration of thermal effect comprising: a container sealed to the atmosphere; a first thermally reactive chemical solute disposed within said container; a first rupturable solvent packet disposed within said container; a first solvent disposed within said first solvent packet; a second rupturable solvent packet disposed within said container; a second solvent disposed within said second solvent packet; a first rupturable solute packet disposed within said container; a second thermally reactive chemical solute disposed within said first solute packet; a second rupturable solute packet disposed within said container; a third chemically reactive solute disposed within said second rupturable solute packet; wherein each of the first and second solvents, first, second and third thermally reactive solutes are chemically separated, and wherein at least two of the first, second and third thermally reactive solutes are different from each other.
In yet another embodiment, the invention provides for a thermal pack adapted to extend the duration of thermal effect having first and second containers each sealed to the atmosphere and from the other, each of said first and second containers comprising: a first thermally reactive solute disposed within said container; a rupturable solvent packet disposed within the container; a solvent disposed within said solvent packet; a rupturable chemical solute packet disposed within said container; a second thermally reactive solute disposed within said rupturable solute packet; wherein each of the solvent, first and second thermally reactive solutes are chemically separated until use and wherein the first thermally reactive solute is different from the second thermally reactive solute.
In each of the above embodiments, a cold pack contains endotherm-producing solutes when reacted with the solvent or solvents. Likewise, a hot pack contains exotherm-producing solutes when reacted with the solvent or solvents.
Another aspect of the invention provides a method of applying thermal treatment to a body comprising: a) selecting a thermal pack adapted to extend the duration of thermal effect comprising a container sealed to the atmosphere, a first thermally reactive chemical solute disposed within said container, a rupturable solvent packet disposed within said container, a solvent disposed within said solvent packet, a rupturable solute packet disposed within said container, a second thermally reactive chemical solute disposed within said solute packet, wherein each of the solvent, the first and second thermally reactive solutes are chemically separated and wherein the first thermally reactive solute is different from the second thermally reactive solute; b) rupturing solvent packet so as to combine with first solute; c) rupturing the solute packet thereby combining the second solute with the solvent; and d) applying the thermal pack to the body.
The invention further provides for a method of applying thermal treatment to a body comprising: a) selecting a thermal pack adapted to extend the duration of thermal effect comprising a container sealed to the atmosphere, a first thermally reactive chemical solute disposed within said container, a rupturable solvent packet disposed within the container, a solvent disposed within the solvent packet, a first rupturable solute packet disposed within the container, a second thermally reactive chemical solute disposed within the first solute packet, a second rupturable solute packet, a third thermally reactive chemical solute disposed within the second rupturable solute packet, wherein each of the solvent, first second and third thermally reactive solutes are chemically separated and wherein at least two of the first second and third thermally reactive solutes are different from each other; b) rupturing solvent packet so as to combine said solvent with said first solute; c) rupturing the first solute packet thereby combining the second solute with the solvent; d) rupturing the second solute packet thereby combining the third solute with the solvent; and e) applying the thermal pack to the body.
The invention also provides for a method of applying thermal treatment to a body comprising: a) selecting a thermal pack adapted to extend the duration of thermal effect comprising a container sealed to the atmosphere, a first thermally reactive chemical solute disposed within the container, a first rupturable solvent packet disposed within the container, a first solvent disposed within the rupturable solvent packet, a second rupturable solvent packet disposed within the container, a second solvent disposed within the second rupturable solvent packet, a first rupturable solute packet disposed within the container, a second thermally reactive chemical solute disposed within the first rupturable solute packet, container, second rupturable solute packet disposed within the container, a third thermally reactive chemical solute disposed within the second rupturable solute packet, wherein each of the first and second solvents, first second and third thermally reactive solutes are chemically separated, and wherein at least two of the first, second and third thermally reactive solutes are different from each other; b) rupturing the first solvent packet so as to combine said solvent with said first thermally reactive solute; c) rupturing the first solute packet thereby combining the second thermally reactive solute with the first solvent; d) rupturing the second solvent packet thereby combining the second solvent with the first and second solutes; e) rupturing the second solute packet thereby combining the third solute with the first and second solvent; and f) applying the thermal pack to the body.
Yet another aspect of the invention provides for a method of applying thermal treatment to a body comprising a) selecting a thermal pack adapted to extend the duration of thermal effect comprising first and second containers each sealed to the atmosphere and from the other, each of said first and second containers comprising a first thermally reactive chemical solute disposed within said container, a rupturable solvent packet disposed within said container, a solvent disposed within said solvent packet, a rupturable solute packet disposed within said container, a second thermally reactive chemical solute disposed within said rupturable solute packet, wherein each of the solvent, first and second thermally reactive solutes are chemically separated and wherein the first thermally reactive solute is different from the second thermally reactive solute; b) rupturing solvent packet in the first container so as to combine said first solvent with said first solute; c) rupturing the solute packet in the first container thereby combining the second solute with said solvent; d) applying the thermal pack to the body; e) rupturing the solvent packet in the second container so as to combine said solvent with said first solute; f) rupturing the solute packet in the second container thereby combining the second solute with the solvent; and g) reapplying the thermal pack to the body.
It will be understood that the step of applying the thermal pack to the body can occur at any point after the initiation of the thermal reaction resulting from the combination of the solvent with the solute(s), irrespective of the various possible rupturing sequences. The thermal treatment can be in the form of either cold or heat therapy.